Image display apparatuses capable of displaying a 3D image include, for example, a liquid crystal shutter system, a polarization system, and other systems. The liquid crystal shutter system displays images for left eye and right eye with binocular parallax, on a flat panel display or the like in a time-division manner. A viewer views a 3D image while wearing liquid crystal shutter glasses that operate in conjunction with the images displayed in a time-division manner. The liquid crystal shutter system is also referred to as a frame sequential system. The polarization system displays an image for left eye using light polarized in a first direction and an image for right eye using light polarized in a second direction different from the first direction, the images having binocular parallax. A viewer views a 3D image while wearing polarization glasses that transmit light for the left eye and light for the right eye that are different in polarization direction from each other. In both the systems, the viewer views images with binocular parallax through the viewer's left and right eyes, and can have stereoscopic perception by virtue of the binocular parallax.
Besides, a parallax barrier system, a lenticular lens system, and other similar systems are 3D image display apparatuses that allow viewers to view 3D images with the naked eye without wearing special glasses. The parallax barrier system is provided with a parallax barrier in front of a flat panel display or the like to separate the pixels of the display into pixels viewable by a left eye and pixels viewable by a right eye, and thereby can present binocular parallax images to the left and right eyes. Likewise, the lenticular lens system is provided with a lenticular lens in front of a flat panel display or the like, and thereby can present binocular parallax images to left and right eyes. The parallax barrier and lenticular lens are referred to as parallax optical elements.
As a 3D image display apparatus that allows a 3D image to be viewed with the naked eye, a 3D image display apparatus using a stack of screens has been devised. Non Patent Literature 1 discloses a method of using a stack of two screens to allow a 3D image to be perceived in front of the front one of the two screens or behind the rear one of the two screens, beyond a space between the two screens. “Front” refers to the viewer side of the screens. “Rear” refers to the opposite side of the viewer with respect to the screens.